To stretch the SCM, you'll need to fix the muscle attachment points at the sternum using the palms of your hands. Apply firm pressure to the sterno-clavicular joint and then slowly lift your chin away from your chest and then tilt to one side. Hold for 30 seconds. Relax, and then repeat the stretch on the other side. Sometimes the SCM can hold trigger points which refer pain into the temple and back of the eye, leading to migraines or headaches. Stretching the SCM may help to reduce tension in the muscle and break down some of the muscle adhesions.
